341 results about "Grid-tie inverter" patented technology

The invention relates to a grid connected inverter control method based on hysteresis modulation under the unbalanced grid voltage condition. The control method comprises that the voltage of a dc bus is detected, and a reference active power value is calculated via a PI (Proportion Integration) regulator; the positive sequence components and the negative sequence components of the grid voltage under a two-phase rotating coordinate system are obtained by processing three phases of detected grid voltages via coordinate conversion and positive/negative sequence component decomposition; three phases of instantaneous reference-current values are obtained from the reference active power value and the positive and negative sequence components of the grid voltage via calculation, coordinate conversion and the like; and finally, the three phases of instantaneous reference-current values are compared with three phases of practical current values, a certain hysteresis width is set, and driving pulses are emitted in a hysteresis control principle. The control method requires no parameters of grid connected filtering reactors, and only includes the PI regulator, thereby providing convenience for construction realization; and under the unbalanced grid voltage condition, the stability of instantaneous grid power can be effectively ensured, the voltage fluctuation of the dc bus can be lowered, and the stability of the grid connected inverters is improved.

The invention discloses a reactive power and voltage control method for grid-connected inverters of a large photovoltaic power station. The method comprises steps as follows: a voltage reference unit gives reference voltage uref to a voltage control point; a reactive power setting unit is used for comparing actual voltage of the voltage control point with the reference voltage to obtain voltage deviation, and reactive power reference quantity Qref required by maintaining voltage of the voltage control point is automatically acquired through a PID (proportional-integral-derivative) controller; a reactive power distribution unit automatically performs reactive power distribution between SVG (scalable vector graphics) and each photovoltaic power generation unit; the grid-connected inverters in the photovoltaic power generation units adopts distribution in equal proportion of reactive capacity. According to the method, coordinated control of a reactive power compensation device of the photovoltaic power station and the photovoltaic inverters is sufficiently utilized, grid-connected point voltage fluctuation of the photovoltaic power station is reduced, reactive power support is provided for a power grid, and voltage stability of a weak grid is improved; meanwhile, reactive power is distributed according to line loss of the photovoltaic power generation units, and active loss of the photovoltaic power station is reduced; therefore, the reactive power and voltage control method facilitates safe, economic and stable operation of the large photovoltaic power station accessing the weak grid.